The synthesis of low-toxic photosensitizers with an optimal ratio of fluorescence and singlet oxygen generation intensity (theranostics) is an urgent task. Dipyrromethene difluoroborates (BODIPYs) occupy a significant place in this area of research. We present the results of the synthesis, structural analysis, study of the chromophore, fluorescent and generation characteristics of BODIPYs, substituted with bromine atoms at the alpha,alpha-, 13,13-and 13 ',13 '- positions of the molecule, their photo-and thermal stability, as well as the features of aggregation behavior in a mixed solvent THF-water. The results obtained were analyzed in comparison with non-halogenated compounds. It has been established that the introduction of bromine atoms into the BODIPY molecule quenches the fluorescent intensity and enhances the singlet oxygen generation. (alpha-Br)2-and (13-Br)2-substituted BODIPYs can be considered as potential theranostics with a predominant bioimaging function, while (13 '-Br)2-BODIPY exhibits a photosensitizer function to a greater extent. Symmetric bromination of BODIPY has a little effect on photo-and thermal stability compared to unsubstituted analogues. The studied bromine substituted boron(III) dipyrromethenates are characterized by the formation of non-fluorescent H-aggregates in a mixed THF-water solvent with a water content in the mixture above 70%.

The design of biocompatible photosensitizers with an optimal combination of intense fluorescence and generation of singlet oxygen is a complex and urgent task. The article presents the results of synthesizing, analyzing the structure, and examining the chromophoric, fluorescent, and generation characteristics of new dimeric bis(beta-Br-BODIPY) (1), as well as the features of its encapsulation in ZIF-8 zeolite framework and solubilization by Pluronic (R) F127 micelles. The photophysical characteristics of brominated dimer 1 were analyzed in comparison with non-halogenated dimers bis(beta-H-BODIPY) (2), bis(beta-CH3-BODIPY) (3), as well as dibromo-substituted mononuclear analogue beta,beta-dibromo-BODIPY (4). Dye 1 exhibits efficient fluorescence (from 53 to 72%) and O-1(2) generation (from 19 to 42%) in solutions of nonpolar and weakly polar solvents. Dimerization leads to a high sensitivity of the fluorescence and generation characteristics of the halogenated dimer 1 to the solvent. The advantage of dimer 1 is a significantly lower tendency to aggregate compared to monomer 4. The conditions for the encapsulation of dye 1 in ZIF-8 nanoparticles and Pluronic (R) F127 micelles were determined and their structural and spectral characteristics were analyzed.

The development of bifunctional theranostic agents based on biocompatible organic luminophores is a priority for the scientific community. We have obtained new mono-Br-substituted BODIPYs (Br-BDPs) with an optimal combination of fluorescence quantum yield (0.48 divided by 0.63) and singlet oxygen generation quantum yield (0.32 divided by 0.51) in different nature solvents. A detailed analysis of the structure of alpha-Br-BDP, beta-Br-BDP, and beta'-Br-BDP dyes, their spectral properties depending on the position of the bromine atom attachment and the solvent nature, as well as the aggregation behavior of the dyes in water/THF solvent mixture are presented. We also selected the conditions for the host-guest encapsulation of beta-Br-BDP in zeolitic imidazolate framework (ZIF-8). The resulting nanoscale beta-Br-BDP@ZIF-8 delivery systems exhibit intense fluorescence. The release of the beta-Br-BDP luminophore from the beta-Br-BDP@ZIF-8 systems into model lipid structures in phosphate buffer pH 5.0 - 6.0 occurs on average after 24 - 50 h. These results form the basis for the further development of new theranostic drugs based on Br-BDP luminophores for fluorescence diagnostics (FD) and photodynamic therapy (PDT).

Unsymmetrically substituted boron(III) and zinc(II) dipyrromethenates were synthesized in high yields, and the physico-chemical investigation results of them are presented. Comparative analysis of luminescence properties in a series of various organic solvents, photo- and thermal stability was carried out depending on the molecular structure. For the first time it was established that the methyl group absence in α-, β- or β′-position of one of the pyrrole fragments changes properties of pentamethyl-dipyrromethene ligands and complexes differently. It is shown unsubstituted α- or β-position of one pyrrole cycle leads to a hypsochromic shift of the maximum of the intense absorption band and free β′-position – to bathochromic shift. In the general case, the fluorescence quantum yield of BODIPY reaches 99% and depends little on the solvent properties. However, BODIPY unsubstituted in one of the α-position showed a sharp decrease of the fluorescence quantum yield upon going from non-polar solvents to polar. Unsymmetrically substituted zinc(II) dipyrromethenates are characterized by low value of the fluorescence quantum yield, the fluorescence almost completely quenching in weakly polar and polar solvents. It is found that the unsymmetrically substitution increases photostability of boron(III) and zinc(II) complexes but decreases their thermal stability in solid state.